Sleep problems can be experienced in many ways, and range from difficulty falling asleep, maintaining sleep throughout the night, or waking too early or too often. Most people will experience some trouble sleeping at some point in their lives, with less sleep associated with long work days, commuting times, increases in evening or night work, and overuse of television, computers, or the internet [322–325]. Sleep disturbances have been associated with the use of, and withdrawal from, AOD; in particular, alcohol [326, 327], cannabis [327, 328], tobacco [329], caffeine [330, 331], opioids [327, 332], and cocaine [327, 333]. Moreover, AOD use is associated with a higher likelihood of developing sleep disorders such as insomnia, nightmares, sleep-related breathing disorders, and circadian rhythm disorders [334, 335]. Although some people report using substances to promote sleep [336], in general, the direction of the relationship is not well understood. It remains unclear as to whether sleep problems are an additional risk factor contributing to a person’s AOD use, whether the use of AOD contributes to sleep disturbances, or both [337]. Sleep problems are also common among people with mental health conditions, including those with major depressive, generalised anxiety, post-traumatic stress, and bipolar disorders [338, 339].
Better understood are the poor health outcomes associated with insufficient sleep quality and duration. The quality and duration of sleep has been linked to chronic disease, with insufficient sleep and poor sleep quality associated with higher body mass [340, 341], weight gain [342–344], obesity [342, 343, 345], diabetes [346], CVD [347, 348] and premature mortality [349–351]. Recent research suggests that the ideal amount of sleep varies with age [352]. For adults aged between 18–64 years, the recommended duration of daily sleep is between seven and nine hours [353], with the risk of chronic diseases, obesity, diabetes, hypertension, and CVD associated with both too little (i.e., less than 6 hours) and too much sleep (i.e., more than 9 hours) [354–358].
Sleep quality and maintenance is equally as important as sleep duration. The American Academy of Sleep Medicine has identified four stages of sleep, the first three of which are non-rapid eye movement (NREM; N1-N3), and the fourth stage rapid eye movement (REM) sleep [359]. Slow wave, or deep sleep, occurs in N3 and is considered the most restorative stage of sleep for executive functioning, typically occurring earlier in the sleep cycle, within an hour of falling asleep [360]. With regard to interventions that may improve sleep quality and quantity, evidence from systematic reviews supports the use of exercise [361, 362], cognitive behaviour therapy (CBT [363–365]), acceptance and commitment therapy (ACT [366]), mindfulness meditation [367], psychoeducation focusing on sleep hygiene [368], smartphone applications targeting sleep disturbances (e.g., CALM [369, 370]), muscle relaxation [365], music [371], aromatherapy [372], and environmental modifications (e.g., the use of ear plugs and a sleep mask [365, 373]). Of these interventions, exercise, CBT, ACT, smartphone applications, and muscle relaxation have been evaluated among people with either mental and/or AOD use disorders. However, mindfulness meditation, psychoeducation focusing on sleep hygiene, music, aromatherapy, and environmental modification have yet to be evaluated among people with either of these disorders. Moreover, none of these interventions have been evaluated among people with co-occurring disorders.
The American Academy of Sleep Medicine [374] recommends the healthy sleep habits outlined in Table 22.